sedimentary

Chert / River Stone

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs); Color: Grey, black, tan, and brown; Luster: Waxy to dull; Texture: Microcrystalline with a conchoidal fracture pattern; Specific Gravity: 2.65.

Hardness: 6
Color: Grey, black, tan, and brown
Luster: Waxy to dull

Identified July 3, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Grey, black, tan, and brown; Luster: Waxy to dull; Texture: Microcrystalline with a conchoidal fracture pattern; Specific Gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments. This specific specimen has been rounded and smoothed by water transport in a river or coastal setting.

Uses & applications

Historically used for stone tools (arrowheads/scrapers) due to its sharp fracture edges. Today it is used in construction aggregate and as decorative landscaping gravel.

Geological facts

Chert was one of the most important materials for early humans because its conchoidal fracture allows it to be knapped into extremely sharp edges. It is sometimes called flint when found in chalk or limestone deposits.

Field identification & locations

Identify in the field by its hardness (will scratch glass), waxy luster on fresh surfaces, and smooth, rounded water-worn shape. Commonly found in riverbeds and glacial deposits.